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If you mean you can't start the computer up with it plugged in then I had a similar issue not long ago, which was easily remedied starting the computer up without it plugged in.
If you mean the computer crashed when you plug the external in you have some more serious issues, my first port of call would be to check the hard drive on a different computer, if it shut that one down too or didnt work for whatever reason, then you need to contact the manufacturer/reseller.
If it is just your computer that shuts down (crashes?) when trying to use it then you will probably need to post some fairly detailed info and hope somebody can help you fix the issue.